The reflections of objects in water are no less dependant on the laws of perspective, or of vision, than the instances already enumerated. If the water be raised to the level of the ground beyond it, we lose all advantage of reflection from the distant ground or trees: this is the case with pieces of water near the house, in many places, for all ponds, on high ground, present a constant glare of light from the sky; but the trees beyond can never be reflected on the surface, because the angle of incidence and the angle of reflection are always equal: and the surface of the water will always be a perfect horizontal plane. This I shall farther explain by the following lines [fig. 48]. The spectator at a, in looking on the upper water, will see only sky; because the angle of incidence b, and that of reflection C being equal, the latter passes over the top of the trees d, on lower ground: but the same spectator a, in looking on the lower water, will see the trees e reflected on its surface, because the line of reflection passes through them, and not over them, as in the first instance.
